Shonen

Shōnen manga (少年漫画?) refers to manga marketed to a male audience roughly between the ages of 10 and 18. Examples include Dragon Ball, Naruto, Bleach, Detective Conan, One Piece, Rurouni Kenshin, InuYasha, Yu Yu Hakusho, Yu-Gi-Oh, D.Gray-Man, and Fullmetal Alchemist.
Shōnen (少年) manga (漫画) is typically characterized by high-action, often humorous plots featuring male protagonists. The camaraderie between boys or men on sports teams, fighting squads and the like is often emphasized. Attractive female characters with exaggerated features are also common (see fan service), but are not a requirement; Dragon Ball Z, for example, has only a few such characters. After the case of Tsutomu Miyazaki, depictions of violence and sexual matters became more highly regulated in manga in general, but especially in shonen manga.[1] The art style of shōnen is generally less flowery than that of shōjo manga, although this varies greatly from artist to artist, and some artists draw both shōnen and shōjo manga.
Beyond shōnen manga, manga for men (university age and up) is called seinen manga. Despite a number of significant differences, many Western fans do not make a distinction between shōnen manga and seinen manga. This may be because very few seinen manga have been published outside of Japan. In Japan, many older men read shōnen magazines because of their ease in reading during commutes to and from work on trains. Consequently, in Japan, shōnen manga magazines are the most popular manga magazines.
(text from Wikipedia)